Crop Tolerance and Weed Management Systems in Imidazolinone-Tolerant Corn (Zea mays L.)¹

Abstract

Field studies were conducted in 1997 and 1998 to evaluate the efficacy of imidazolinone weed management systems and crop tolerance of imidazolinone-tolerant (IT) corn to imazapic. Imazapic (36 and 72 g/ha) was evaluated when applied PRE; early postemergence (EPOST), when corn was at the two- to three-leaf stage; and late postemergence (LPOST), when corn was at the six- to eight-leaf stage. Imazapyr + imazethapyr EPOST and metolachlor + atrazine followed by (fb) primisulfuron LPOST were evaluated as commercial standards. Imazapic at 36 g/ha EPOST controlled johnsongrass, Texas panicum, smellmelon, and ivyleaf and entireleaf morningglory at least 93% when adequate rainfall occurred. Devil's claw was controlled at least 85% with imazapic EPOST or LPOST at either rate. Imazapic at 36 g/ha EPOST and LPOST controlled eclipta 88 and 91%, respectively. Yellow nutsedge was controlled >91% with imazapic LPOST, which was superior to imazapic applied EPOST. Broadleaf signalgrass was controlled 94% with imazapic at 72 g/ha LPOST, which was significantly higher than other herbicide treatments. Imazapic at 36 and 72 g/ha applied PRE under moisture stress resulted in reduced weed control; but when adequate rainfall occurred, weed control was generally similar to that of EPOST and LPOST applications. Imazapic crop response at 72, 105, 140, and 211 g/ha applied at EPOST and LPOST was evaluated in two IT corn hybrids. Crop response varied with soil and environmental conditions and application timings. Imazapic at 72, 105, and 140 g/ha EPOST resulted in crop injury 33 to 55% at 6 wk after planting (WAP) in a coarse soil; however, crop injury decreased to <20% at 12 WAP. Low crop injury (<9%) was observed at 12 WAP in a clay soil. Imazapic applied LPOST resulted in lower crop injury than EPOST application. Corn plant height and yield were not affected by any imazapic treatment.

Herbicide Systems for Control of Horse Purslane (Trianthema portulacastrum L.), Smellmelon (Cucumis melo L.), and Palmer Amaranth (Amaranthus palmeri S. Wats) in Peanut

“…Imazapic at 0.04 to 0.07 kg/ha controlled greater than 90% smellmelon in corn regardless whether applied PRE, EPOST, or LPOST (Thompson et al, 2005). Grichar et al (2001) reported that imazapic provided consistent control ($ 85%) of citronmelon (Citrullus lanatus var.…”

“…Smellmelon can be a problem at peanut harvest as the melon can become broken apart when run through the combine and increase drying time because of the high moisture content of the melon itself (author's personal observation). In IMI-tolerant corn (Zea mays L.), Thompson et al (2005) reported that imazapic at 0.07 and 0.14 kg ai/ha applied either preemergence (PRE), early POST, or late POST controlled smellmelon greater than 90%. Tingle and Chandler (2004) reported that smellmelon control was at least 93% with low-, medium-, and high-input herbicide systems.…”

Postemergence Weed Control in Peanut Using Reduced Rate or Combinations of Imazapic and Imazethapyr

“…In previous studies, imazapic at 0.04 to 0.07 kg/ha controlled smellmelon greater than 90% in peanut or corn ( Zea mays L.) regardless whether applied PRE, EPOST, or LPOST (9,16). Grichar et al (8) reported that imazapic provided consistent control (≥ 85%) of citronmelon ( Citrullus lanatus var.…”

Influence of Adjuvants on Efficacy of Postemergence Herbicides Commonly Used in Peanut (Arachis hypogaea L.)

“…In 2013, using Induce with the low dose of imazapic did reduce C. melo control compared to the use of no adjuvant or ETA. Imazapic at 0.04-0.07 kg/ha controlled greater than 90% C. melo in corn (Zea mays L.) regardless whether applied either preemergence, early POST or late POST [42], while Grichar [43] has seen similar results in peanut with imazapic POST applications. The high humidities at application timing may have been a factor in the excellent control [44].…”